Dadar to Chennai - the a/c compartments are at the back, with HA1 the last a/c before the general one. The vestibule to the general compartment is closed shut, so unreserved cannot enter the main bogies of the train.
Also, left out the couple of things from my last write up. The toilets were clean, I guess because of the regular cleanings. The cabins are supposed to be cleaned twice, once in the morn and once in the eve. but the cleaners showed up twice before lunch. So we had a bunch of trash after lunch that we could not dispose of and had to be left in the trash can (yes!!, there is one each cabin). The trash can...
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itself can be pushed out of sight below the counter just as you enter the cabin on each side. BTW, There is also a shelf just above one of the counters to keep your small luggage and also hang your shirts. In one of the stations (I think Guntakal), there was a cleaning crew on the platform cleaning the outside of the a/c windows - this is what I call progress, may be this could be carried over to the interior of the whole train...
To check the speed, go to Nokia Drive (beta). Once it locks on to the GPS, it will show the speed. Although the app kept putting us on the road next to the track (if there was one) since it has been designed as a driving app. there are also some apps available for ipad/iphone that can show you the speed. I downloaded one such app (free, but shows speed only in mph) for my ipad and the speeds between the two devices matched. Google maps on ipad are quite detailed showing tracks between cities. Nokia drive maps are not so detailed in "foresty" areas.